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What is alkaline soil?
Also known as Usara soils they are so-called because they consist of an alkali group of metals and induce basicity.
Alkali soil or alkaline soil or sometimes also referred to as alkaline sodic soil is the soil carrying pH greater than 8.5, hence basic. It consists of great amounts of calcium, magnesium, and sodium ions.
Derived from the Arabian word al qalīy, it refers to calcine soils (burnt ashes, a product of calcination process that is a process of heating substances at high temperatures in lack of or absence of oxygen but below its melting point so as to remove dirt).
Areas prone to it
They occur in arid and semi-arid regions, and in waterlogged and swampy areas. These are more widespread in western Gujarat, deltas of the eastern coast, and in Sunderban areas of West Bengal. Soils form a white hard coating on the surface.
Why is it problematic to agriculture?
Low infiltration capacity leading to waterlogging particularly in dry periods it poses a great challenge to cultivation.
Low productivity.
Reduced nutrients especially micronutrient availability thus causing problems like chlorosis ( Iron deficiency).
Restrain plant growth by restricting water supply to the roots.
This could lead to phosphorus and zinc deficiencies.
Plants have less ability to extract the essential nutrients from the soil.
Symptoms
It includes drying up of leaves. The color of leaves ranges from white to brownish red. The growth of the plants is restrained. Its symptoms could appear the same as that of nitrogen deficiency so it is preferred to bring the soil to the lab and go for its testing where pH can be taken into consideration.
Causes of soil becoming alkaline
There are many causes of soil alkalinity which may be either natural or man-made
The presence of minerals causes alkalinity a great deal naturally.
Emission of droplets of sodium chloride from cooling towers in industries in the vicinity of agricultural land.
Cao particles released from power plants dissolve in water and are passed to rivers through the rain. Water from rivers while going through lime softening makes itself devoid of Ca2+ and Mg2+ ions and increases sodium content making soil alkaline.
Application of softened water in irrigation.
The industrial release includes a good deal of sodium salts which enter river basins increasing sodicity and passing to cultivated river basins.
Sodium salts present in the ash also pose the problem of alkalinity.
Solutions to get rid of alkaline soil
1. Planting of high pH tolerant plants ensure success in plantings and poses a lesser hazard to micronutrients deficiency like asparagus, lenten rose, beech tree, garlic, okra, cauliflower, etc.
2. Raised beds can be created using commercial potting soils.
3. Additives such as sulfur, organic matter, and fertilizers can be used.
4. Addition of gypsum to alkaline soil.
5. Deep plowing and incorporating the calcareous subsoil into the topsoil would reduce the top surface’s white hardening.
6. Poly house or shade netting also helps.
7. Plantation of Barilla plants i.e. salt-tolerant species would help.
Addition of sulfur
Utah state university's extension suggests the annual addition of elemental sulfur at the rate of 6 to 10 pounds per 1,000 square feet of area. To reach an appropriate pH level you must try adding sulfur to the soil. It gets converted to sulfuric acid through the action of soil bacteria that oxidize it to sulfate ions.
Addition of organic matter
Organic matter such as peat reduces the soil pH because the microbes present in organic matter decompose and create carbonic acid. However, manure increases the pH.
Addition of fertilizers
Ammonium sulfate and fertilizers lower the soil pH. For instance, sulfur coated urea not only lowers the soil pH but also adds nitrogen to the soil.
Addition of gypsum
Gypsum could be added to alkaline soil as gypsum is the source of sulfur and reduces Al toxicity. There must be enough natural drainage to the underground, or else an artificial subsurface drainage system must be present, to allow leaching of the excess sodium by percolation of rain and /or irrigation water. In extensively cultivated areas like Punjab and Haryana farmers are advised to add gypsum to their soils to solve the problem of salinity in the soil.
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